The present invention relates to an actuating mechanism, and more particularly to an actuating mechanism for rotating a micro-mirror in a photoelectric device such as a laser scan display or an optical switch.
Micro-mirrors are more and more popular in photoelectric industry, and become essential for many photoelectric devices. For example, referring to FIG. 1, micro-mirrors 11 are used in a laser scan display, which consists of a laser source 101, an optical wave guide 102, a lens 103, a silicon substrate 104, a support plate 105 and another lens 106, to guide laser beams to the scan points, and actuating devices 12 are used to adjust the rotation angles of the micro-mirrors 11. In another example, a micro-mirror array 13 consisting of plural micro-mirrors and respective actuating devices are used in a multi-port optical switch, which includes plural optical fibers 14 and a reflective mirror 15, to adjust the light directions, as shown in FIG. 2.
U.S. Pat. No. 5,867,297 discloses an actuating mechanism for rotating a micro-mirror, which is as shown in FIG. 3 and incorporated herein for reference. In this actuating mechanism, the assembling operation is complicated, and the micro-hinges 21 are subject to being worn. In addition, the rotation of the mirror 20 is limited to one dimension, as indicated by the arrow A.
Please refer to FIG. 4A which is a schematic diagram showing another conventional actuating mechanism for rotating a micro-mirror. The micro-mirror 22 itself can be rotated in a first dimension indicated by the arrow A, and can be further rotated in a second dimension indicated by the arrow B with an auxiliary ring 24. When the micro-mirror 22 is rotated in either of the dimensions B1 and B2, the rotation angle is confined within a small range because of the presence of a substrate 20 thereunder. In this conventional actuating mechanism, the micro-mirror 22 itself functions as an electrode which interacts with another electrode 201 or 202 formed on the substrate 20 to control the rotation of the micro-mirror 22, as shown in FIG. 4B. The interaction between the mirror electrode 22 and the electrode 201 or 202 is generated due to the electrostatic force therebetween. As understood, the distance D between the two electrodes 22 and 201/202 should be small enough to generate a sufficient electrostatic force to rotate the micro-mirror 22 about the pivot 23. Accordingly, the angle range xcex8 will be limited.
Further, owing to the frequent rotation, it is possible for the micro-mirror to be distorted by the actuating force so that the reflection function of the mirror may be adversely effected.
Therefore, an object of the present invention is to provide an actuating mechanism for rotating a micro-mirror within a relatively large angle range.
Another object of the present invention is to provide an actuating mechanism for rotating a micro-mirror, in which the micro-mirror is strengthened with a grid ring.
According to a first aspect of the present invention, an actuating mechanism for rotating a micro-mirror includes a substrate formed thereon a first recess region; a shaft secured to the micro-mirror for rotating the micro-mirror therewith in the first recess region; a first actuator mounted on the substrate beside the first recess region for providing a first actuating force; a first linking rod device including a first linking rod and a first fulcrum positioned between a first and a second portions of the first linking rod, the first portion being flexibly connected to the shaft, and the second portion being coupled to the first actuator; a second actuator mounted on the substrate beside the first recess region opposite to the first actuator for providing a second actuating force; and a second linking rod device including a second linking rod and a second fulcrum positioned at one end of the second linking rod, the second linking rod including a third portion flexibly connected to the shaft, and a fourth portion coupled to the second actuator; wherein the second and fourth portions are moved in response to the first and second actuating forces to lever the first and third portions via the first and second fulcrums, respectively, thereby rotating the shaft.
In an embodiment, the substrate is a silicon substrate, and the first and second linking rods are made of low stress silicon nitride.
In an embodiment, the first actuator includes a bottom electrode formed on the substrate; a top electrode connected to the second portion of the first linking rod, and formed above the bottom electrode with a gap therebetween; and a power source connected to the bottom and top electrodes for providing a potential difference in order to generate an electrostatic force between the bottom and top electrodes, thereby controlling the size of the gap, and moving the second portion of the first linking rod.
Preferably, the bottom electrode is formed of a doped semiconductor material, and the top electrode is formed of a material selected from a group consisting of aluminum, platinum and gold. More preferably, the first actuator further includes an insulating structure between the bottom and top electrodes.
Similarly, the second actuator may includes a bottom electrode formed on the substrate; a top electrode connected to the fourth portion of the second linking rod, and formed above the bottom electrode with a gap therebetween; and a power source connected to the bottom and top electrodes for providing a potential difference in order to generate an electrostatic force between the bottom and top electrodes, thereby controlling the size of the gap, and moving the fourth portion of the second linking rod. The bottom electrode is formed of a doped semiconductor material, the top electrode is formed of a material selected from a group consisting of aluminum, platinum and gold, and the second actuator further includes an insulating structure between the bottom and top electrodes.
Preferably, the substrate is further formed thereon a second recess region for providing a movement space for the first and second linking rods.
Preferably, the shaft is coupled to both of the first portion of the first linking rod and the third portion of the second linking rod via a coupler.
The actuating mechanism according to the present invention is suitable for rotating a micro-mirror made of aluminum. The micro-mirror is preferably strengthened by providing therearoud a grid ring to prevent from distortion due to the actuating forces.